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Table 2 Comparison of the characteristics of patients with positive and negative EGFR mutation cobas test results

From: Tumour content ratio matters for detecting epidermal growth factor receptor mutation by cobas test in small biopsies; a retrospective study

 

EGFR positive n = 100

EGFR negative n = 32

p value

EGFR mutation with PCR clamp, n (%)

  

0.012

 19del

55 (55)

10 (31)

 

 L858R

36 (36)

21 (66)

 

 L861Q

4 (4)

0 (0)

 

 G719X

5 (5)

1 (3)

 

 T790 M

1 (1)a

0 (0)

 

Tumour histological type, n (%)

  

0.52

 Adenocarcinoma

96 (96)

32 (100)

 

 Squamous cell carcinoma

3 (3)

0 (0)

 

 NSCLC with morphological squamous cell and adenocarcinoma patterns

1 (1)

0 (0)

 

TKI therapy, n (%)

87 (87)

23 (72)

0.29

Gefitiniba

52 (60)

12 (52)

 

Erlotiniba

16 (18)

7 (30)

 

Afatiniba

18 (21)

4 (17)

 

Naquotiniba

1 (1)

0 (0)

 

Number of chemotherapies before TKI therapy, n (%)a

  

.08

 0 regimen

56 (64)

9 (39)

 

 1 regimen

27 (31)

10 (43)

 

 2 regimens

3 (3)

3 (13)

 

 3 regimens

1 (1)

1 (4)

 

Response to TKI, n (%)b

  

0.59

 PR/CR

64 (74)

15 (65)

 

 SD

8 (9)

4 (17)

 

 PD

8 (9)

3 (13)

 

 NA

7 (8)

1 (4)

 

PFS for the first TKI therapy, m, median (95%CI)

12.2 (9.3–16)

12.4 (7.3–13.3)

0.24

Tumour content ratioc, %, median (IQR)

19 (11–32)

11 (5–18)

0.002

  1. Abbreviations: EGFR epidermal growth factor receptor, NSCLC non-small cell carcinoma, TKI tyrosine kinase inhibitors, PR partial response, CR Complete Response, SD Stable Disease, PD Progressive Disease, NA not available, PFS progression free survival, IQR interquartile range
  2. aDouble positive with L858R and T790 M by PCR clamp test and only L858R by cobas test
  3. bAnalysis of 110 patients who received TKI therapy. 23 of the patients showed negative results with the cobas method
  4. cTumour cell count over the total cell count conducted on a slide-mounted biopsy sample